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Biomedical subjects

David M Baguley

Publications and source records attributed to David M Baguley.

At least 19 recordsLinked to original sources
PubMed2005

Optimizing the clinical fit of auditory brain stem implants.

OBJECTIVE: To develop and implement a new audiological fitting procedure for auditory brain stem implants (ABIs), based on an efficient algorithm, and to compare it with two procedures presently used in clinical practice. DESIGN: First, the different procedures were compared by using computer models and simulations with normal-hearing subjects (N = 4). This allows for an analysis of the accuracy of the procedures in a way that is not possible when testing ABI users. The root-mean-square error between the order estimated by the procedure and the true order was calculated. In addition, ABI users (N = 2) were tested with the new procedure to see if it could be successfully applied in clinic. The degree of variability of their results across runs and sessions was analyzed. RESULTS: The tests of the normal-hearing subjects showed that our proposed procedure required significantly fewer trials (22 on average) than procedures presently used in clinic (with 76 and 234 trials on average for the two other procedures tested) to produce the same degree of accuracy. Computer modeling also demonstrated this advantage. Additional testing showed this advantage was maintained under a variety of conditions relevant to the clinic. The two patients tested were able to use this procedure with success, even though they were poor at discriminating the pitch of electrodes. The patients showed results consistent with having about 4 to 5 discriminable groups of electrodes with the 12 to 14 electrodes tested. CONCLUSIONS: The proposed procedure requires fewer trials to produce a clinically useful result and is well tolerated in the clinic. An additional advantage is that it allows testing to be broken down into several "blocks," each containing a small number of trials. If the variability between blocks is small, information can be combined across blocks to increase the accuracy of the result. If the variability is large, perhaps between blocks on different days, this may reflect a significant change in the percepts generated by the implant, and signal to the clinician that a significant alteration in the fitting is required. We recommend its use in ABI user fitting and in cochlear implant fitting when pitch ranking is problematic.

Adult↗
PubMed2005

The inhibitory effect of intravenous lidocaine infusion on tinnitus after translabyrinthine removal of vestibular schwannoma: a double-blind, placebo-controlled, crossover study.

OBJECTIVE: Intravenous infusion of lidocaine has previously been demonstrated to have a transient inhibitory effect on tinnitus in 60% of individuals. The site of action has variously been proposed as the cochlea, the cochlea nerve, and the central auditory pathways. To determine whether a central site of action exists, this study investigated the effect of intravenous infusion of lidocaine in individuals with tinnitus who had previously undergone translabyrinthine excision of a vestibular schwannoma, which involves division of the cochlear nerve. STUDY DESIGN: Double-blind, placebo-controlled, crossover study. SETTING: University hospital. PATIENTS: Patients who had undergone translabyrinthine removal of a unilateral, sporadic, and histologically proven vestibular schwannoma in the last decade and who had reported postoperative tinnitus at follow-up were identified from a departmental database. Sixteen patients participated (12 men and 4 women). The mean age (+/- standard deviation) of the patients was 58 +/- 8.6 years, and the meantime since operation was 24.3 +/- 7.3 months. INTERVENTION: Solutions of 2% lidocaine hydrochloride and sodium chloride 0.9% were prepared in identical randomized vials. The volume required for 1.5 ml/kg body weight lidocaine was calculated, and this volume was given over 5 minutes for either vial. Blood pressure, pulse oximetry, and cardiac monitoring were set up and performed throughout the infusions. All investigators were blinded. OUTCOME MEASURES: Patient-completed visual analogue scale measures of tinnitus intensity, pitch, and distress, performed before infusion, 5 minutes after infusion onset, and 20 minutes after infusion onset. RESULTS: A significant difference (Wilcoxon signed-rank test, p < 0.05) between placebo and lidocaine infusion conditions was demonstrated for change in visual analogue scale estimates (preinfusion versus 5 min postinfusion) of tinnitus loudness (p = 0.036), pitch (p = 0.026), and distress (p = 0.04). No significant difference between placebo and lidocaine infusion conditions was demonstrated for change in visual analogue scale estimates (preinfusion versus 20 min postinfusion) of tinnitus loudness (p = 0.066), pitch (p = 0.173), and distress (p = 0.058). The indication is of a short-lasting inhibitory effect on tinnitus of lidocaine infusion compared with saline placebo in patients who have undergone translabyrinthine excision of a vestibular schwannoma. CONCLUSION: Intravenous infusion of lidocaine has a statistically significant inhibitory effect on tinnitus in patients who have previously undergone translabyrinthine removal of a vestibular schwannoma. The site of action of lidocaine in this instance must be in the central auditory pathway, as the cochlear and vestibular nerves are sectioned during surgery, and this finding has important implications for the task of identifying other agents that will have a similar tinnitus-inhibiting effect.

Adult↗
PubMed2005

Change in tinnitus handicap after translabyrinthine vestibular schwannoma excision.

OBJECTIVE: To evaluate the change in tinnitus handicap after translabyrinthine vestibular schwannoma excision. STUDY DESIGN: Prospective administration of the Tinnitus Handicap Inventory (THI) preoperatively and at 3 and 12 months postoperatively. SETTING: : A tertiary referral neuro-otology clinic. PATIENTS: A total of 149 patients from a series of 170 consecutive patients who had vestibular schwannomas excised between May 1998 and July 2002 and who had completed THIs preoperatively and at 3 and 12 months postoperatively. INTERVENTIONS: Translabyrinthine excision of a unilateral sporadic vestibular schwannoma. MAIN OUTCOME MEASURES: THI scores. RESULTS: The number of patients with moderate or severe handicap was 21 (14%) in the preoperative group and 21 (14%) in the 12-month postoperative group. No significant differences in group data were found comparing (by Wilcoxon signed rank test) preoperative data with 3 months postoperative data (p = 0.09), preoperative data with 12 months postoperative data (p = 0.09), and 3 months postoperative data with 12 months postoperative data (p = 0.33). Considering group data, tinnitus handicap is neither alleviated nor exacerbated by translabyrinthine surgery. The application of the validated 20-point criteria for significant change in the status of an individual patient indicates that tinnitus handicap was worse in 10 (6.5%), unchanged in 129 (87%), and better in 10 (6.5%). CONCLUSIONS: The findings of the current study can be used during preoperative patient counseling. In particular, the clinician is now able to take an informed and positive stance about the tinnitus handicap to be expected postoperatively.

Adult↗
PubMed2005

A novel mutation of COL2A1 resulting in dominantly inherited rhegmatogenous retinal detachment.

PURPOSE: To determine the molecular defect in a family with autosomal dominant rhegmatogenous retinal detachment (DRRD), and to investigate missplicing as a possible phenotypic modifier of mutations in COL2A1. METHODS: Clinical examination of the family and linkage analysis using markers flanking COL2A1 and COL11A1, the known loci for Stickler syndrome; mutation screening of COL2A1; construction of splicing reporter minigenes and transfection into cultured cells; and RT-PCR analysis of reporter specific transcripts. RESULTS: A family with DRRD showed no systemic clinical signs (skeletal, orofacial, or auditory) usually associated with Stickler syndrome. Linkage analysis excluded COL11A1 as the disease locus but could not exclude COL2A1. Mutation screening of COL2A1 identified a novel G118R mutation in type II collagen. Transfection of minigenes carrying mutations associated with DRRD (G118R, R453X, and L467F) into cultured cells detected no missplicing of mRNA from mutant constructs. CONCLUSIONS: Mutations outside the alternatively spliced exon 2 region of COL2A1 can also result in an ocular only phenotype. There was no evidence that missplicing modifies the phenotype of these mutations, suggesting that the minimal or absent systemic features demonstrated by the G118R and L467F mutations are the result of the biophysical changes imparted on the collagen molecule.

Alternative Splicing↗
PubMed2004

Laser excision of glomus tympanicum tumours: long-term results.

The purpose of this study was to evaluate the long-term results of laser excision of glomus tympanicum tumours in a series of patients who had been referred to the senior author (DAM) in a retrospective case review. Nine patients underwent complete excision of their glomus tympanicum tumours using a Diode or KTP laser. There were no cases of tumour recurrence. There were no complications during the peri- or postoperative period. Follow-up time was 31.8 months. In our experience, laser excision can be performed with minimal bleeding and morbidity, and it provides excellent tumour control in glomus tympanicum surgery.

Adolescent↗
PubMed2004

Tinnitus and cochlear implantation.

Tinnitus is a common experience, but there is very marked heterogeneity of aetiology, perception and the extent of distress among individuals who experience tinnitus. In view of this, a modern approach to tinnitus should consider homogeneous groups of individuals. This review considers tinnitus experiences in patients undergoing cochlear implantation, this being of interest because the prevalence of tinnitus in this patient group prior to surgery may shed some light on the link between cochlear dysfunction and tinnitus Second, any change in tinnitus experience as a result of electrode placement surgery or cochlear implant activation has relevance for patient counselling and informed consent. Finally, in recent tinnitus retraining therapy literature there has been the suggestion that unilateral sound therapy for tinnitus patients may set up an unhelpful asymmetry of input to the auditory system, with possible exacerbation of contralateral tinnitus. Unilateral cochlear implant use represents the most dramatic asymmetry possible and hence is a test of that hypothesis. Relevant papers (n = 32) were identified from literature databases. The standard of reporting tinnitus results was inconsistent. Tinnitus is experienced by up to 86% of adult cochlear implant candidates, but is not universal and is only troublesome in a small proportion (reported as 27% in one study). Electrode insertion may induce tinnitus in a small (up to 4%) number of patients, but this is rare. Cochlear implant device use is associated with reduction of tinnitus intensity and awareness in up to 86% of patients, and rarely with exacerbation (up to 9%). There are some indications in the literature that the more complex the simulation strategy, the larger that effect. Specifically, unilateral cochlear implant use was generally associated with reduction of contralateral tinnitus (in up to 67% of individuals) rather than exacerbation, and so the assertion that unilateral sound therapy for tinnitus is contraindicated is not proven.

Cochlea↗
PubMed2004

Change in hearing handicap after translabyrinthine vestibular schwannoma excision.

OBJECTIVE: To evaluate the change in hearing handicap after translabyrinthine vestibular schwannoma excision. STUDY DESIGN: Prospective administration of the Hearing Handicap Inventory preoperatively and at 3 and 12 months postoperatively. SETTING: A tertiary referral neurootology clinic. PATIENTS: A total of 119 consecutive patients who had vestibular schwannomas excised between May 1998 and July 2002 and who had completed Hearing Handicap Inventories preoperatively and at 3 and 12 months postoperatively. INTERVENTIONS: Translabyrinthine excision of a unilateral sporadic vestibular schwannoma; pre- and postoperative hearing therapy and rehabilitation. MAIN OUTCOME MEASURES: Hearing Handicap Inventory scores. RESULTS: Sixty-one percent of patients showed no change in their hearing handicap between preoperative and 3-month postoperative measures. Fifty-eight percent showed no change between preoperative and 12-month postoperative measures. Twenty-five percent of patients had a worsening in their hearing handicap when comparing preoperative and 12-month postoperative scores, and these patients were those with a better hearing class preoperatively. Seventeen percent of patients showed an improvement in their hearing handicap over this same time period, and the reasons for this remain unclear. Neither age nor tumor size had an effect on change in hearing handicap. CONCLUSIONS: The findings of the current study can be used during preoperative patient counseling. In particular, the clinician is now able to take an informed and positive stance about the hearing handicap to be expected postoperatively.

Audiometry, Pure-Tone↗
PubMed2004

Clinical evaluation of the vector algorithm for neonatal hearing screening using automated auditory brainstem response.

A novel auditory brainstem response (ABR) detection and scoring algorithm, entitled the Vector algorithm is described. An independent clinical evaluation of the algorithm using 464 tests (120 non-stimulated and 344 stimulated tests) on 60 infants, with a mean age of approximately 6.5 weeks, estimated test sensitivity greater than 0.99 and test specificity at 0.87 for one test. Specificity was estimated to be greater than 0.95 for a two stage screen. Test times were of the order of 1.5 minutes per ear for detection of an ABR and 4.5 minutes per ear in the absence of a clear response. The Vector algorithm is commercially available for both automated screening and threshold estimation in hearing screening devices.

Algorithms↗
PubMed2003

Change in dizziness handicap after vestibular schwannoma excision.

OBJECTIVE: To evaluate the change in dizziness handicap after translabyrinthine vestibular schwannoma excision. STUDY DESIGN: Prospective administration of the Dizziness Handicap Inventory preoperatively and at 3 and 12 months postoperatively; retrospective review of case notes. SETTING: A tertiary referral neuro-otology clinic. PATIENTS: A total of 100 consecutive patients who had vestibular schwannomas excised between June 1998 and November 2001 and who had completed Dizziness Handicap Inventories preoperatively and at 3 and 12 months postoperatively. INTERVENTIONS: Translabyrinthine excision of a unilateral sporadic vestibular schwannoma; preoperative and postoperative generic vestibular rehabilitation exercises. MAIN OUTCOME MEASURES: Dizziness Handicap Inventory scores. RESULTS: For most patients, dizziness handicap does not worsen postoperatively. However, for those in whom it does, dizziness handicap becomes significantly worse between preoperative and 3-month postoperative time points but then does not continue to decline. Tumor size, sex, and magnitude of preoperative canal paresis significantly affect the degree of change in handicap. Age, the presence of central vestibular system abnormalities, and the nature of the patient's principal presenting symptom have no effect on this handicap change. CONCLUSIONS: These findings help the clinician in counseling the patient preoperatively about dizziness handicap to be expected postoperatively. In particular, the clinician is now able to take an informed and positive stance in the event of a severe canal paresis preoperatively.

Aged↗
PubMed2003

Hyperacusis.

Explore the source record for details and available documents.

Persons with Disabilities↗
PubMed2003

Audiologic presentation of cerebellopontine angle cholesteatoma.

OBJECTIVE: The aim of this study was to examine the audiologic presentation of patients with cerebellopontine angle (CPA) cholesteatoma. DESIGN: Retrospective case review. SETTING: Neuro-otologic tertiary referral centre. METHODS: The study population consisted of 11 patients with CPA cholesteatomas. The patients underwent a standard audiologic investigation in the preoperative setting, which consisted of pure-tone audiometry, speech audiometry, and auditory brainstem response (ABR). MAIN OUTCOME MEASURES: The audiologic parameters that were analyzed were the pure-tone threshold, pure-tone average (PTA), and speech discrimination scores (SDSs). The morphology and latency of the ABR were evaluated. In addition, the clinical and radiologic presentations of the lesions were reviewed. RESULTS: The mean PTA in the diseased ear was 22.6 dB HL (SD 18.2), whereas in the contralateral ear, it was 19.1 dB HL (SD 19.6). In 4 patients, the hearing loss was asymmetric, with the diseased ear being the worse ear. The mean SDS was 82.28% in the affected ear and 95.28% in the contralateral ear. ABR was abnormal in 9 of 10 cases (90%), with only the affected ear being abnormal in 4 cases. In the other 5 cases, the ABR was bilaterally abnormal. CONCLUSIONS: CPA cholesteatomas are very slow-growing lesions that involve the eighth cranial nerve. The paucity and insidious onset of symptoms mean that the diagnosis is often late, permitting the lesions to reach impressive dimensions at the time of diagnosis. Although magnetic resonance imaging represents the gold standard in the diagnosis of these lesions, ABR proved to be of value in the assessment of the auditory pathway, especially in those patients referred with a vague symptomatology and with normal hearing.

Adult↗
PubMed2003

Contraindications to the Dix-Hallpike manoeuvre: a multidisciplinary review.

The Dix-Hallpike manoeuvre is widely used in the diagnosis of positional vertigo and is regarded as safe. The manoeuvre involves a degree of neck rotation and extension, and consequently one might expect there to be some patients, particularly those with neck problems, in whom the manoeuvre is contraindicated. The term 'neck problem', however, encompasses a whole range of conditions, including soft tissue disorders, cervical spondylosis, prolapsed intervertebral disk, and severe rheumatoid arthritis with cervical instability. These in turn will give rise to a variety of symptoms, which will vary from minimal pain or stiffness to severe pain or complete immobility, and, in some cases, neurological deficit. Clarification is therefore needed to establish the point at which any neck pain or stiffness ceases to be a minor problem and becomes a contraindication to performing the Dix-Hallpike manoeuvre. This paper clarifies this issue by discussing the issue of absolute contraindications and proposing a simple functional assessment of neck mobility which can be performed prior to performing the Dix-Hallpike manoeuvre. Relative contraindications such as back pathology, vertebrobasilar ischaemia (posterior circulation ischaemic disease), nerve root compression and medical fitness are also discussed.

Humans↗
PubMed2002

Management strategies in neurofibromatosis type 2.

The objective of this study was to review the experience of the Neurotology and Skull Base Surgery Unit of Addenbrooke's Hospital in Cambridge, England, in the management of patients with neurofibromatosis type 2 (NF2). This was a retrospective review of the institution's series conducted at a neurotological tertiary referral centre. Over a 17-year period (1984-2001), 35 patients with NF2 were managed. These patients presented with multiple cranio-spinal neoplasms, including 62 cerebellopontine angle tumours of which 59 were vestibular schwannomas (nine patients with unilateral tumours and 25 patients with bilateral tumours). Clinical presentation, diagnosis and patient management were reviewed. The outcome parameters measured were tumour progression, the incidence of complications (hearing deterioration and facial nerve palsy) and the need for secondary intervention. Five vestibular schwannomas were treated with stereotactic radiosurgery (gamma-knife), all of which showed evidence of progression in size and/or deterioration in hearing. Thirty-one VS were conservatively treated with annual surveillance. In nine cases, the tumours had a follow-up shorter than 6 months and were therefore excluded from the results. In 13 cases the VS did not progress in size, and the hearing remained stable, while in the remaining nine cases, tumour progression was evident. In fifteen cases, surgery was performed at the authors' institution. In 11 cases a translabyrinthine approach was adopted, and in the remaining four cases a retrosigmoid approach was preferred. In all these cases, tumour removal was total and facial nerve function was House-Brackmann grade I-III in 55%. Successful hearing preservation was elusive in those patients in whom a hearing preservation approach was attempted. NF2 remains an extremely challenging disorder for the neurotologist and the patient alike. Early diagnosis offers distinct advantages to the patients, their families and the community at large. Of the treatment modalities, surgery unequivocally offers the most superior tumour control. Hearing preservation remains a challenge in these patients, but is optimised by the early detection of tumours in the NF2 patient.

Adolescent↗
PubMed2002

Mechanisms of tinnitus.

The generation of tinnitus is a topic of much scientific enquiry. This chapter reviews possible mechanisms of tinnitus, whilst noting that the heterogeneity observed within the human population with distressing tinnitus means that there may be many different mechanisms by which tinnitus can occur. Indeed, multiple mechanisms may be at work within one individual. The role of the cochlea in tinnitus is considered, and in particular the concept of discordant damage between inner and outer hair cells is described. Biochemical models of tinnitus pertaining to the cochlea and the central auditory pathway are considered. Potential mechanisms for tinnitus within the auditory brain are reviewed, including important work on synchronised spontaneous activity in the cochlear nerve. Whilst the number of possible mechanisms of tinnitus within the auditory system is considerable, the identification of the physiological substrates underlying tinnitus is a crucial element in the design of novel and effective therapies.

Aminoglycosides↗